A Curious Case of Measles

Why are they coming back?


The World Health Organization (WHO) declared measles eliminated in the United States in 2000. Recently, however, various outbreaks now threaten that status. Our project uses data from the Center for Disease Control (CDC), Google, and Twitter to explore whether trends in the digital frenzy around measles correspond with actual cases.

History

Regular documentation of measles cases in the United States can be traced back to 1912, when it became complusory for health facilities to report cases. Incidences of measles, and related diseases such as Rubella and Mumps, dropped dramatically after the invention of the MMR vaccine. A great accomplishment of modern medicine, the vaccine is 97% effective in preventing measles contraction in children who receive both doses prior to the age of six.



Today

####Immunization Rates and Current Cases

In spite of the efficacy of the MMR vaccine, parents in the United States are increasingly electing not to vaccinate their children. This, in turn, lowers “herd immunity,” putting unvaccinated children and immunocompromised individuals at risk. In December 2018, cases of measles began to rise as international travelers exposed to the disease abroad came in contact with disease-vulnernable populations. Cases have now occurred in 22 states, with the most active outbreaks ongoing in California, New York, Oregon, and Washington.



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####What are people in New York saying?
As measles cases have spread in the United States, so has the online dicussion surrounding the condition. We analyzed measles-related Google search terms and Twitter content, first to identify time trends and top concerns, then to compare how pro- versus anti-vaccination opinions differ.
Spikes in Google searches for measles by New York residents parallel outbreaks, with the 2015 California outbreak and today’s cases visualized below.
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On Twitter, the most common term associated with the #measles hashtag, aside from the disease itself, was vaccination. This top term hints at the controversy that, in part, is fueling the current outbreak’s spread.

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Tweet terms from anti-vaxxers are highlighted in red, while tweets from a pro-vaccine point of view are featured in blue.
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School Focus

This section examines immunization surveys collected at the school level in New York State, beginning with the 2012-2013 school year.

First, we examine the trends in exemption rates over time and look at immunization rates at the County level.

Average Immunization Rates by Counties

We identify the counties that have immunization rates less than 94, again as this is the benchmark for successfully establishing herd immunity. There are 15 counties that meet this criteria. The bar chart below shows a list of counties that are at risk of measles contagion.

The top 5 counties in New York with low measles vaccination rates are Montgomery, Yates, Allegany, Cattaraugus, and Seneca.

The interactive map below shows the schools in New York that have immunization rates below the ideal threshold needed to achieve herd immunity. We have identified 574 schools as being risky

Type of Risky Schools

The most common type of school in the risky dataset is private schools.

Text Analysis of Risky Schools

Christian is the most frequent term.

The most frequent words associated with schools that have low immunization rates is words like “christian”, “yeshiva”, and “montessori”. This refers to relgious institituions and alternative learning institutions.

Text Analysis of Riskiest Schools

FALSE [1] 91 14

There are 91 schools where no child is vaccinated against measles.

Again, we see references to religious instituions like “muhammed”, “menonite”, and “amish”.

Focusing on New York City

There are 109 schools in the New York City ‘at-risk’ category. Every school below the 94% immunization threshold in NYC is a private school. Let’s look at them on a static plot.

Let’s look at the medical exemption rate and the religious exemption rates


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Examining 2019 Measles Mandate

Under the NYC Measles Mandate, four zipcodes will be affected: 11205, 11206, 11211 and 11249.

FALSE [1] 44 14

This covers only 44 schools, whereas we have identifed 109 schools in New York City that are at risk. Let’s perform a text analysis on the school names to see what patterns emerge.

This is very interesting because we previously saw that christian was the most frequent word in the risky dataset.

The barchart shows that many of the identified schools are well above the threshold for herd immunity.

FALSE [1] 25 14

In fact, more than half of the schools in the zipcodes identified by the NYC Health Department have vaccination rates that are adequate for herd immunity.

Using Data to improve NYC Policy

Let’s look at average measles immunization rates by zipcodes. We will simply look at the top 5.

Only 1 zipcode in the list above, (i.e. 11221), was correctly identified by the NYC Health Department. The zipcode 10026, with an average immunization rate of 47.6% across schools was not identified as a risky region.

Let’s look at which schools fall in the zip codes we identified above.

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We argue that a mandatory measles vaccination policy must address the 14 schools above in the top 5 zipcodes we identified.